JPH08100700A - Cam shaft supporting structure for engine - Google Patents

Abstract

PURPOSE: To facilitate the assembling of a cam shaft to a cylinder head. CONSTITUTION: A cam shaft 29 is provided with a first shaft end journal part 52a and a first through a third intermediate journal parts 53a, 53b, 53c, and those journal parts are respectively supported to the bearing hole 451 of the upper end wall 45 of a cylinder head 6 and to the bearing holes 491 , 501 , 511 of intermediate bearing bosses 49, 50, 51. The radius of the opening 481 for inserting the cam shaft of the bearing holes 451 , 491 , 501 , 511 and the lower end wall 48 of the cylinder head 6 are r5 >r4 >r3 >r2 >r1 , and also the maximum radius of an intake cam 54 and an exhaust cam 55 is smaller than the radiuses r4 , r3 , r2 of the bearing holes 491 , 501 , 511 . Thereby, the cam shaft 29 can be smoothly inserted from the opening 481 for inserting a cam shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine camshaft supporting structure for supporting a camshaft having a plurality of valve cams and journals on an intermediate bearing formed on a cylinder head.

[0002]

2. Description of the Related Art When a cam shaft is supported in a cam chamber provided in a cylinder head of an engine, if the cam shaft has a short total length such as a cam shaft of a single cylinder engine or a two cylinder engine,
Both ends thereof can be supported on the side wall of the cylinder head. However, a camshaft of a large engine having three or more cylinders, which has a long overall length, causes bending only by supporting both ends, so that a journal part formed in the middle part thereof is provided in the middle part of the cylinder head. It is designed to be supported by bearings.

In the intermediate bearing, an intermediate bearing boss formed integrally with the cylinder head, a bearing cap that is connected to the intermediate bearing boss with a bolt to hold the journal portion of the camshaft, and an integrally formed cylinder head. Some cam shafts are inserted into the bearing holes formed in the intermediate bearing boss and the journals are fitted into the bearing holes.

[0004]

The former requires a bearing cap and bolts, which increases the number of parts, while the latter requires a bearing cap and bolts, which reduces the number of parts. It However, in the latter case, when inserting the cam shaft into the bearing hole of the intermediate bearing boss, the valve cam interferes with the bearing hole having a diameter smaller than the maximum diameter, so a notch for passing the valve cam. Has to be formed in the bearing hole, and the cam shaft must be inserted while rotating the cam shaft to match the phase of the valve operating cam with the phase of the notch, and there is a problem that the assembling workability is low.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a camshaft support structure for an engine, which enables easy assembly of the camshaft to the cylinder head.

[0006]

In order to achieve the above-mentioned object, the invention described in claim 1 forms a cam shaft insertion opening and a plurality of intermediate bearing bosses in a cylinder head, and a plurality of valve operating valves. By inserting a camshaft having a cam and a plurality of journal portions from the camshaft insertion opening, the camshaft of an engine in which a plurality of journal portions are rotatably supported in bearing holes formed in a plurality of intermediate bearing bosses, respectively. In the support structure, the radius of each bearing hole is larger than the maximum radius of the valve cam, and the radius of each bearing hole is gradually reduced from one closer to the camshaft insertion opening to one farther from it. .

The invention described in claim 2 is, in addition to the structure of claim 1, a bearing for supporting the cam shaft by the intermediate bearing boss, and a bearing for supporting a rocker arm shaft having a diameter smaller than the cam shaft. The thickness of the intermediate bearing boss in the vicinity of the bearing hole supporting the rocker arm shaft is set to be smaller than the thickness of the intermediate bearing boss in the vicinity of the bearing hole supporting the cam shaft. Characterize.

[0008]

According to the structure of claim 1, the cam shaft is inserted through the cam shaft insertion opening formed in the cylinder head, and the plurality of journal portions thereof are fitted into the bearing holes of the plurality of intermediate bearing bosses formed in the cylinder head. The cam shaft is supported by the cylinder head by the combination. At this time, since the radius of each bearing hole is larger than the maximum radius of the valve cam, the valve cam does not interfere with the bearing hole, and the radius of each bearing hole is close to the cam shaft insertion opening. The cam shaft can be smoothly inserted because the distance from the object gradually decreases.

According to the second aspect of the present invention, since the thickness of the intermediate bearing boss is large in the vicinity of the bearing hole for supporting the rocker arm shaft, a sufficient support area for the small diameter rocker arm shaft can be ensured. Since the intermediate bearing boss has a small thickness in the vicinity of the bearing hole that supports the camshaft, it is possible to prevent the supporting area of the large-diameter camshaft from becoming excessive.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 7 show an embodiment of the present invention. FIG. 1 is an overall side view of an outboard motor, FIG. 2 is an enlarged cross-sectional view of an essential part of FIG. 1, and FIG. -3 line enlarged arrow view, FIG. 4 is FIG.
4 is a sectional view taken along line 4-4, FIG. 5 is an enlarged view of an essential part of FIG. 2, FIG. 6 is a sectional view taken along line 6-6 of FIG. 5, and FIG.

As shown in FIGS. 1 and 2, the outboard motor O is
A mount case 2 coupled to the upper portion of the extension case 1 is provided, and an in-line 4-cylinder 4-cycle engine E is supported on the upper surface of the mount case 2. An under case 3 having an open upper surface is coupled to the mount case 2, and an engine cover 4 is detachably attached to an upper portion of the under case 3. An under cover 5 is attached between the lower edge of the under case 3 and the upper edge of the extension case 1 so as to cover the outside of the mount case 2.

The engine E includes a cylinder block 6, a crankcase 7, a cylinder head 8, a head cover 9, a lower belt cover 10 and an upper belt cover 11, and the cylinder block 6 and the crankcase 7 are provided on the upper surface of the mount case 2. Supported. Four cylinders 12a ₁ , 12a ₂ , 12 formed in the cylinder block 6
Pistons 13 ... Are slidably fitted in b ₁ and 12b ₂ , respectively, and each piston 13 is connected to a crankshaft 15 arranged in the vertical direction via a connecting rod 14.

The flywheel 1 is attached to the lower end of the crankshaft 15.
The drive shaft 17 connected together with 6 extends downward inside the extension case 1, and the lower end thereof is a gear case 18
It is connected to a propeller shaft 21 having a propeller 20 at its rear end via a bevel gear mechanism 19 provided inside. The lower end of the shift rod 22 is connected to the front part of the bevel gear mechanism 19 in order to switch the rotation direction of the propeller shaft 21.

One cam shaft 29 parallel to the crank shaft 15
Is rotatably supported by the cylinder head 8, and a timing belt 33 is wound around a crank pulley 30 provided at the upper end of the crank shaft 15 and a cam pulley 31 provided at the upper end of the cam shaft 29. A generator 36 including a stator 34 and a rotor 35 is provided above the crank pulley 30, and a starting pulley 37 for manually starting the engine E is provided above the generator 36. The cam pulley 31, the tension pulley 32, the timing belt 33, the generator 36, and the starting pulley 37 are housed inside the lower belt cover 10 and the upper belt cover 11. An oil pump 38 that pumps oil from an oil pan 39 is provided at the lower end of the cam shaft 29.

A swivel shaft 25 is fixed between an upper mount 23 provided on the mount case 2 and a lower mount 24 provided on the extension case 1, and a swivel case 26 rotatably supporting the swivel shaft 25.
Is supported by a stern bracket 27 attached to the stern S so as to be vertically swingable via a tilt shaft 28.

Next, the cam shaft 29 supported by the cylinder head 8 and its supporting structure will be described with reference to FIGS.

As is apparent from FIGS. 3 to 6, the cylinder head 8 has a cylinder block connecting surface 41 connected to the cylinder block 6 and a head cover connecting surface 42 connected to the head cover 9, and the cylinder block connecting surface is formed. Four combustion chambers 43 ... Are recessed on the surface 41 side, and a valve operating chamber 44 is recessed on the head cover coupling surface 42 side.

A cam is provided on the upper end wall 45 of the cylinder head 8.
Bearing hole 45 for supporting the upper end of the shaft 29 ₁And the intake rocker
Bearing hole 45 for supporting the upper end of the arm shaft 46₂And exhaust
Bearing hole 45 for supporting the upper end of the rocker arm shaft 47₃And
It is formed. On the other hand, the lower end wall 48 of the cylinder head 8
Is a cam shaft insertion opening 4 into which the cam shaft 29 is inserted during assembly.
8₁And a shaft that supports the lower end of the intake rocker arm shaft 46
Receiving hole 48₂And supports the lower end of the exhaust rocker arm shaft 48
Bearing hole 48₃And are formed. Assemble the camshaft 29
The cam shaft insertion opening 48 is₁No oil
Pump housing 38 of pump 38₁Fit together.

The cylinder head 8 is integrally provided with three intermediate bearing bosses 49, 50, 51 so as to project into the valve operating chamber 44. The intermediate bearing bosses 49, 50, 51 are provided with camshafts 29, respectively. Bearing holes 49 ₁ for supporting the intermediate part of
50 ₁ , 51 ₁ , bearing holes 49 ₂ , 50 ₂ , 52 ₂ supporting the intermediate portion of the intake rocker arm shaft 46, and bearing holes 49 ₃ , 5 supporting the intermediate portion of the exhaust rocker arm shaft 47.
0 ₃ , 52 ₃ are formed. The intake rocker arm shaft 46 and the exhaust rocker arm shaft 47 are non-rotatably fixed.

As is apparent from FIG. 5, the cam shaft 29 has a first shaft end journal portion 52a fitted in the bearing hole 45 ₁ of the upper end wall 45 and a cam shaft insertion opening 48 _{1 of the} lower end wall 48.
Together and a second axial end journal portion 52b to be fitted to the bearing hole 49 ₁ of the intermediate bearing bosses 49, 50, 51,
The first intermediate journal portion 53a, the second intermediate journal portion 53b, and the third intermediate journal portion 53c, which are fitted to the respective 50 ₁ and 51 ₁ , are provided. The cam shaft 29 is provided with a flange 63 near the lower end thereof, and the flange 63 is axially positioned by being locked to a locking member 64 (see FIG. 1) which is bolted to the cylinder head 8.

The cam shaft 29 has the above-mentioned five journal parts 52.
a, 52b, 53a, 53b, 53c, 4 corresponding to each cylinder 12a ₁ , 12a ₂ , 12b ₁ , 12b _2.
And four exhaust cams 55 are provided, and the fuel pump is provided between the intake cam 54 and the exhaust cam 55 of the cylinder 12a ₂ and between the intake cam 54 and the exhaust cam 55 of the cylinder 12b _2. Drive cams 56,5
6 is provided.

As is apparent from FIGS. 3 and 4, the intake rocker arm 57 pivotally supported on the intake rocker arm shaft 46.
Is the intake cam 54 and the cylinders 12a ₁ and 12a ₂
The exhaust rocker arms 59, which are in contact with the intake valves 58 provided for each of the two, are pivotally supported by the exhaust rocker arm shaft 47.
Exhaust valve 60 provided for each of a ₁ , 12a ₂ ...
Abut.

The pump drive rods 61, 61 abutting against the two pump drive cams 56, 56 are connected to the two fuel pumps 62, 62 provided on the side wall of the cylinder head 8, and therefore the fuel pump 62. , 62 are driven by the cam shaft 29.

Four bearing holes 4 for supporting the camshaft 29
Of 5 ₁ , 49 ₁ , 50 ₁ , 51 ₁ , the radius r ₁ of the bearing hole 45 ₁ of the upper end wall 45 farthest from the cam shaft insertion opening 48 ₁ of the lower end wall 48 of the cylinder head 8 is the smallest. , The radii r ₂ , r ₃ , r ₄ of the bearing holes 49 ₁ , 50 ₁ , 51 ₁ of the intermediate bearing bosses 49, 50, 51 gradually increase as they approach the lower end wall 48. The radius r ₅ of the camshaft insertion opening 48 ₁ of the lower end wall 48 is larger than the radius r ₄ of the bearing hole 51 ₁ of the intermediate bearing boss 51. That is, r ₁ <r ₂ <r ₃ <r ₄ <r ₅ is established.

The four bearing holes 45 ₁ , 49 ₁ , 5
The first shaft end journal portion 52a and the first to third intermediate journal portions 53a to 5 of the cam shaft 29 which are fitted to 0 ₁ , 51 _1.
The radius of 3c is such that the bearing holes 45 ₁ , 4 into which they are fitted.
R ₁ , r ₂ , equal to the radius of 9 ₁ , 50 ₁ , 51 ₁ ,
r ₃ and r ₄ . In addition, the second shaft end journal portion 52b of the cam shaft 29 has the cam shaft insertion opening 48 of the lower end wall 48.
Since the pump housing 38 ₁ between the inner circumference of ₁ is interposed, the diameter r ₅ 'is smaller than r ₅ is the radius of the cam shaft insertion opening 48 _1.

Bearings of the intermediate bearing bosses 49, 50, 51
Hole 49₁, 50₁, 51₁Radius r ₂, R₃, R_FourDifference
Is about 0.5 mm, which is the smallest of them
Bearing hole 49 of bearing boss 49₁Radius r₂Than each intake
The cam 54, the exhaust cam 55, and the fuel pump drive cam 5
The maximum radius of 6,56 is set small (see FIG. 7).

Therefore, in order to assemble the cam shaft 29 to the cylinder head 8, the cam shaft insertion opening 48 _{1 of the} lower end wall 48 is formed.
When inserting the cam shaft 29 from the intake cam 54, the exhaust cam 55, and the fuel pump drive cams 56, 56, the cam shaft insertion opening 48 ₁ and the bearing holes 49 ₁ , 50 of the intermediate bearing bosses 49, 50, 51. _No interference with ₁ , 51 ₁ ,
The first shaft end journal portion 52a and the first to third intermediate journal 53a~53c of the cam shaft 29, _first bearing hole 45 in the upper end wall 45, respectively, and an intermediate bearing boss 49,50,5
1 bearing holes 49 ₁ , 50 ₁ , 51 ₁ .

Further, the cam shaft insertion opening 48 ₁ has the maximum radius, and the bearing holes 49 of the intermediate bearing bosses 49, 50, 51 are formed.
_Since the radii of ₁ , 50 ₁ and 51 ₁ gradually decrease from the side closer to the camshaft insertion opening 48 ₁ , the first intermediate journal portion 53a has the camshaft insertion opening 48 ₁ and the bearing hole 49 ₁ ,
50 when passing through _1, when the second intermediate journal portion 53b passes through the opening 48 ₁ and the bearing hole 50 ₁ Insert camshaft, further when the third intermediate journal portion 53c is passed through the opening 48 ₁ Insert camshaft , Avoiding the occurrence of interference, camshaft 2
9 can be inserted smoothly.

When the cam shaft 29 is inserted, oil is inserted between the inner circumference of the cam shaft insertion opening 48 ₁ of the lower end wall 48 of the cylinder head 8 and the outer circumference of the second shaft end journal portion 52b of the cam shaft 29. the pump housing 38 _first pump 38 is fitted to complete the assembly of the cam shaft 29.

As is apparent from FIG. 5, each of the intermediate bearing bosses 49, 50, 51 has a thickness greater than the axial thickness t ₁ on the base end side connected to the main body of the cylinder head 8 in the intake rocker arm shaft 46. And bearing holes 49 ₂ , 50 ₂ , 51 ₂ for supporting the exhaust rocker arm shaft 47; 49 ₃ , 50 ₃ ,
The axial thickness t ₂ on the tip side where 51 ₃ is formed is large. Thus, the intermediate bearing bosses 49, 50, 51 having a bulged front end side can be formed by using a sand core when the cylinder head 8 is cast. Then, the intermediate bearing bosses 49, 50, 51 have a lower hole formed by the sand core, and the lower hole is machined to form bearing holes 49 ₁ , 50 ₁ , 51 ₁ . As described above, by forming the pilot hole with the sand core, the material lost as cutting waste can be reduced.

As described above, the intake rocker arm 46
And bearing hole 4 for supporting the exhaust rocker arm shaft 47
9 ₂ , 50 ₂ , 51 ₂ ; 49 ₃ , 50 ₃ , 51 ₃ are formed in a portion (thickness t ₂ ) of the intermediate bearing bosses 49, 50, 51 having a large axial thickness, and thus the intake rocker arm. It is possible to secure a sufficient support area even if the diameter of the shaft 46 and the exhaust rocker arm shaft 47 is small. On the contrary, the bearing holes 49 ₁ , 50 ₁ , 51 ₁ supporting the large-diameter cam shaft 29 are formed in the portion (thickness t ₁ ) of the intermediate bearing bosses 49, 50, 51 having a small axial thickness. Therefore, even if the cam shaft 29 has a large diameter, the supporting area is prevented from becoming excessive.

Although the embodiments of the present invention have been described in detail above, the present invention can be modified in various ways without departing from the scope of the invention.

For example, in the embodiment, the in-line four-cylinder engine E of the outboard motor O is illustrated, but the present invention can be applied to engines other than the outboard motor O, and three cylinders or five. It can also be applied to engines with more than cylinders.

[0035]

As described above, according to the invention described in claim 1, since the radius of each bearing hole is larger than the maximum radius of the valve cam, the phase adjustment is performed when the cam shaft is inserted. Valve cam does not interfere with each bearing hole without
Also, since the radius of each bearing hole is gradually reduced from the one closer to the camshaft insertion opening to the one farther from it, the camshaft can be inserted smoothly by avoiding the interference between the journal part and the bearing hole. The workability of assembling the camshaft is greatly improved.

According to the invention described in claim 2,
Since the thickness of the intermediate bearing boss near the bearing hole that supports the rocker arm shaft is set larger than the thickness near the bearing hole that supports the cam shaft of the intermediate bearing boss, it is possible to support the small diameter rocker arm shaft. You can secure a sufficient area,
Further, it is possible to prevent the supporting area of the large-diameter cam shaft from becoming excessive.

[Brief description of drawings]

1] Overall side view of the outboard motor

FIG. 2 is an enlarged cross-sectional view of the main part of FIG.

3 is an enlarged sectional view taken along line 3-3 of FIG.

FIG. 4 is a sectional view taken along line 4-4 of FIG.

5 is an enlarged view of a main part of FIG.

6 is a sectional view taken along line 6-6 of FIG.

FIG. 7 is a view in the direction of arrow 7 in FIG.

[Explanation of symbols]

8 Cylinder head 29 Cam shaft 46 Intake rocker arm shaft (rocker arm shaft) 47 Exhaust rocker arm shaft (rocker arm shaft) 48 ₁ Cam shaft insertion opening 49, 50, 51 Intermediate bearing boss 49 ₁ , 50 ₁ , 51 ₁ Bearing Holes 49 ₂ , 50 ₂ , 51 ₂ Bearing holes 49 ₃ , 50 ₃ , 51 ₃ Bearing holes 53a, 53b, 53c Intermediate journal part (journal part) 54 Intake cam (valve cam) 55 Exhaust cam (valve cam)

Claims (2)

[Claims] 1. A cylinder head (8) having a camshaft insertion opening (48 ₁ ) and a plurality of intermediate bearing bosses (49, 50, ₅ ).
1) and inserting a cam shaft (29) having a plurality of valve cams (54, 55) and a plurality of journal portions (53a, 53b, 53c) from the cam shaft insertion opening (48 ₁ ). Allows a plurality of intermediate bearing bosses (49, 50, 5
In the camshaft support structure of the engine in which the plurality of journal portions (53a, 53a, 53a) are rotatably supported in the bearing holes (49 ₁ , 50 ₁ , 51 ₁ ) formed in ₁ ), each bearing hole ( The radius of 49 ₁ , 50 ₁ , 51 ₁ ) is larger than the maximum radius of the valve cam (54, 55) and the radius of each bearing hole (49 ₁ , 50 ₁ , 51 ₁ ) is for camshaft insertion. A camshaft support structure for an engine, which is characterized in that the diameter gradually decreases from the one closer to the opening (48 ₁ ) to the one further away. 2. The intermediate bearing boss (49, 50, 51)
Are bearing holes (49 ₁ , 50 ₁ , for supporting the cam shaft (29),
51 ₁ ) and a bearing hole (49 ₂ , 5) for supporting the rocker arm shaft (46, 47) having a diameter smaller than that of the cam shaft (29).
0 _2, 51 _2; 49 _3, 50 _3, 51 ₃₎ provided with a bearing bore (49 ₂ supporting rocker arm shaft intermediate bearing boss (49, 50, 51) and (46, 47), 5
0 ₂ , 51 ₂ ; 49 ₃ , 50 ₃ , 51 ₃ ) in the vicinity of the thickness of the cam shaft (2) of the intermediate bearing boss (49, 50, 51).
9. The camshaft support structure for an engine according to claim 1, wherein the thickness is set to be larger than the thickness in the vicinity of the bearing holes (49 ₁ , 50 ₁ , 51 ₁ ) for supporting 9).